This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A238582 #19 May 29 2017 20:40:12 %S A238582 1,4,6,1,1,4,12,3,1,8,28,10,1,8,54,82,49,8,1,1,12,95,283,311,91,10,1, %T A238582 12,146,647,1118,451,68,1,16,212,1300,3380,3076,1200,209,20,1,1,16, %U A238582 288,2260,8443,13336,9364,2819,387,20 %N A238582 Number T(n,k) of equivalence classes of ways of placing k 3 X 3 tiles in an n X 9 rectangle under all symmetry operations of the rectangle; irregular triangle T(n,k), n>=3, 0<=k<=2*floor(n/3), read by rows. %H A238582 Andrew Howroyd, <a href="/A238582/b238582.txt">Table of n, a(n) for n = 3..989</a> %H A238582 Christopher Hunt Gribble, <a href="/A238009/a238009_1.cpp.txt">C++ program</a> %e A238582 The first 9 rows of T(n,k) are: %e A238582 .\ k 0 1 2 3 4 5 6 7 8 9 %e A238582 n %e A238582 3 1 4 6 1 %e A238582 4 1 4 12 3 %e A238582 5 1 8 28 10 %e A238582 6 1 8 54 82 49 8 1 %e A238582 7 1 12 95 283 311 91 10 %e A238582 8 1 12 146 647 1118 451 68 %e A238582 9 1 16 212 1300 3380 3076 1200 209 20 1 %e A238582 10 1 16 288 2260 8443 13336 9364 2819 387 20 %e A238582 11 1 20 379 3709 18203 42412 44599 19051 3682 282 %o A238582 (C++) See Gribble link. %Y A238582 Cf. A034851, A226048, A102541, A226290, A238009, A228570, A225812, A238189, A238190, A228572, A228022, A231145, A231473, A231568, A232440, A228165, A238550-A238552, A228166, A238555, A238556, A228167, A238557-A238559, A228168, A238581, A238583, A228169, A238586, A238592. %K A238582 tabf,nonn %O A238582 3,2 %A A238582 _Christopher Hunt Gribble_, Mar 01 2014 %E A238582 Terms corrected and xrefs updated by _Christopher Hunt Gribble_, Apr 27 2015 %E A238582 Terms a(46) and beyond from _Andrew Howroyd_, May 29 2017